Green light ... Kick-Ass and Hit Girl are to return. Photograph: Everett/Rex Features

Kick-Ass was always rather nicely set up for a sequel, what with that open-ended denouement, so it's hardly surprising that Mark Millar, who wrote the original comic book, has been talking up a second film. Speaking to BBC Radio 5 Live, Millar said the film's success on DVD in the US, where it sold 1.4m units in its first week, meant the project was finally greenlit.

"The estimate is that Kick-Ass will do 100 to 150m on DVD based on the American sales, so it'll end up making a $250m (£160m) on a $28m investment," said Millar. "So it should be OK. The sequel's greenlit, we can go ahead and do the follow-up now. The first made so much compared to what it cost, it would be crazy not to."

Millar's announcement, however, has been greeted with a degree of scepticism in the blogosphere, not least because Kick-Ass director Matthew Vaughn and screenwriter Jane Goldman are tied up with preparations for X Men: First Class. In a later interview with MTV, Millar said the film was "probably about nine months away from production starting, at the earliest".

He added: "Matthew's got to do X-Men: First Class. He just wants to get X-Men done next year, then hopefully we'll just go straight into Kick-Ass 2. That's the plan."

Could Millar, who clearly stands to benefit from a second film, be over-egging the biscuit? Probably. Having interviewed him, he's a refreshingly candid chap, saying that film-makers attempting to bring less well-known superheroes to the big screen were "fucked", following the arrival of Kick-Ass's postmodern take. And this is a man who works extensively for Marvel Comics.

The truth probably lies somewhere between the two positions. What we do know is that if Kick-Ass 2 does get made, it will likely centre on Dave Lizewski's encounters with a new breed of wannabe superheroes and supervillains, inspired by his adventures. The film will show Hit Girl struggling to lead a normal life, and I can't imagine there not being a prime role for Christopher Mintz-Plasse as Red Mist.

Millar said in March that he was planning on writing the second book in April. "The idea of Kick-Ass was: what would happen if people in the real world tried to become superheroes?" Millar told IGN earlier this year. "The second one is: what if people tried to be bad guys as a reaction to the superheroes?

Millar adds: "And it's just that simple: The same way these wee guys were contacting each other on Facebook and trying out superhero costumes, what if bad kids started to do this? You've got this horrible Clockwork Orange kind of scenario going on, where these kids are happy-slapping.

"They're out there with their mobile phones dressed up as villains doing horrible things to people, recording it and putting it online. And that becoming massively viral all over the world."

It's a vivid image that one can imagine working well for Vaughn, if the sequel does end up being made. For me, Kick-Ass was an enjoyably throwaway, fluid and vibrant slice of comic-book silliness, which made great viewing on the big screen. I'd very much like to see a sequel. They'd better get a move on though – Chloë Moretz won't stay 13 forever, and a grown-up Hit Girl would rather defeat the object, don't you think?